Numerical Simulation On Noise Reduction Of Axial Flow Fan

The prediction and reduction of aerodynamic noise is one of the most studied research topics due to its significant importance. In this paper, the influences of an improved airfoil on both aerodynamic noise and performance of a low-speed axial fan were studied numerically. In addition, the influences of blade sweep on both aerodynamic noise and performance of a high-speed axial fan in the same way.In present research, steady and unsteady numerical simulation method was employed for the influence of improving the airfoil thickness of the leading edge on the aerodynamic performance and noise radiation of a selected axial fan. Conclusions are drawn out that improving the airfoil thickness of leading edge appropriately benefits the aerodynamic performance of the low-speed axial fan with a small flow rate as well as the stability margin of the fan, meanwhile the vorticity distribution within the channel and static pressure of leaf surface are improved. In the aspect of noise, the blade surface aerodynamic noise and sound field sound pressure level in the blade passing frequency are decreased, which effectively reduces the fan total sound pressure level at far-field.Besides, the effects of blade forward sweep on a selected high-speed axial fan aerodynamic noise and performance were also studied. The results show that: the blade swept of the axial flow fan increases the fan efficiency at off-design conditions, together with its stability range. While compared with a non-swept fan, its total pressure ratio suffers a deficit, which will reduce the Mach number and pressure distribution in spanwise direction. Due to the improvement, the efficiency of the fan running in all conditions improves significantly. At the same time, the forward swept fan reduces the shock intensity and surface static pressure magnitude, improving the air flow in flow passage. The noise and multiple tone noise are perfected effectively by the forward swept fan, which reduces significantly the total sound pressure level lower behind the turbofan, and leads to a relatively weaker reduction in frontcourt of the fan.